TexAQS 2006 TOPAZ Lidar data

August 24 - Final Data

A short flight was intended to test laser/lidar adjustments made the previous
day and fly over the Ronald H. Brown. Flow was light (3-4 m/s) and southwesterly,
becoming even lighter and westerly for about 1 h starting at 1200 CDT. A thundershower
passing to the south of Ellington delayed takeoff, and clouds inland were a problem
for airborne lidar sampling. The flight started out in the clear over the Gulf, and
the lidar performed well. Very low ozone concentrations of approx. 20 ppb or less were
noted over Galveston Bay, but higher concentrations appeared aloft with 60 ppb or
more above 1800 m MSL. Aerosol concentrations were opposite, with high concentrations
below 1 km and low concentrations above ~2 km. Passing northward along the western
shore of Galveston Bay, ozone concentrations increased and the aerosol seemed to
become more vertically mixed. An E-W leg north of the city showed two ozone maxima
of >120 ppb, one representing the ship channel and one the urban center. The ozone
and high aerosol concentrations jumped vertically to ~2400 m downwind of the urban
center, whereas the mixed layer height farther east was more like 1400 m, a probable
urban heat island effect. Ron Brown overpasses occurred at 17:17 and 17:23 CDT.